Okay, so you've decided to give playwrighting a whack, but you are not sure what to write about. Everyone tells you to "write what you know" so you begin to get an idea...
You can write any play except the following:
DO NOT WRITE A WISH-FULFILLMENT STORY OF BUDDING ROMANCE BETWEEN TWO TEENS, ONE OF WHOM BEARS A RESEMBLANCE TO YOU, ONE TO YOUR IDEALIZED MATE.
Don't get me wrong. Teens are good. Romance is good. There is nothing wrong with you for coming up with this idea for a play. After all, a lot of early playwrighting is putting to paper the little conversations you have in your head. And what goes on in your head is often the construction of awesome romances and what you would say to your sweet baboo, if only you could meet him/her. The only thing wrong with this scenario is that EVERYONE shares the same go-to. (I'm specifically targeting the straight, white, upper-middle class American version of this play, which is the one that most typically goes nowhere.) The playwrighting contest will be filled with these gentle scenes of romance, of "I hate you but I secretly love you." As someone who spent 5 years as a judge for South Carolina's student playwrighting contest, I read hundreds of these, and they were never very compelling. The exception to this rule is if you can find what makes this story unique, what reason an audience would have for rooting for these would-be lovers, and a compelling reason for writing the play other than "I wish I had a date because that would be awesome." It would and it will, but that's not enough of a reason to ask an audience to sit captive in your theater and give up their time to watch your theaterical avatar score.
Other Ideas on the Taboo List:
No Plays about not knowing what to write a play about, or anything in which characters in the play come to life and abuse or help the playwright. However, nothing says your play has to be grounded in reality. Crash test Dummies Support group? Slow Day at the Easter Bunny's Office? The untold story of William Howard Taft? Yes.
No Plays about nice people who are sitting around talking about an incident unseen by the audience.
However, this does not mean your characters can't be nice.
No Plays that exist as an excuse for a bunch of strangers to monologue about their reactions to an event (school shooting, death of Elvis, scandal in a small town, etc.) Beginning actors think that monologues are the sign of the most amazing acting, because an actor can "be all dramatic" and not have to sit through their sene partners' lines. Advanced actors know that theater happens in the air between two characters, so dialogue where each character is pursuing a different objective is where it's at.
Dont be afraid of writing what you know: remember, you go to an extremely weird school that could make a great setting for a play that will seem exotic to many. There are plays to be written about the honor code, about friends from widely varying socio-economic backgrounds, about casual racism, "tradition" vs. innovation, conformity, and on and on.
Just keep going back to the most basic building blocks of the theater: the Action. I want to get you to do this, but you want me to do something else. Try not to think in terms of gimmicks or themes or anything bigger than a charcter who has a very strong desire for something.
And for what it's worth, here's what's written on a little piece of paper over my desk:
You have permission to write things that are banal, baffling, and don't work. You don't have permission to leave the page blank.
GOOD LUCK AND GET AFTER IT!